1. Field of the Invention
The present invention is directed to a controller for an engine, and in particular, a controller for a fuel-injected engine which controls the fuel injectors based on a detected intake air pressure.
2. Description of Related Art
In all fields of engine design, there is an increasing emphasis on obtaining more effective emission control, better fuel economy, and at the same time, continued high or higher power output. This trend has resulted in the substitution of fuel injection systems for carburetors as the charge former for internal combustion engines. Typically, fuel injection systems for internal combustion engines receive input from a variety of sensors included on the engine which are configured to output data which reflect the operating conditions of the engine. For example, a fuel-injected engine may include an engine speed sensor, an air temperature sensor, a throttle position sensor, an engine temperature sensor, and an air flow sensor. The controller for the engine monitors each of these sensors to determine the appropriate fuel injection timing and duration corresponding to the detected conditions. Thus, as the accuracy of the sensors and the processing of the data from the sensors is increased, so is the accuracy of the fuel injection duration and timing calculations and the emissions and the fuel efficiency of the engine.
Among the various types of data monitored by the controllers of fuel-injected engines, accurate determination of air flow into the engine poses a unique challenge. Although the flow of induction air into an engine is controlled by a throttle valve, it is imperative to determine the mass flow rate of the induction air into the engine in order to determine the appropriate mass of fuel required to accurately produce the desired air/fuel ratio. In some applications, the mass flow rate of air into the engine is estimated by detecting the absolute pressure within the induction manifold (manifold absolute pressure or "MAP") which is proportional to the total volume of air drawn into the engine. The absolute pressure is then used, in combination with other data collected from various other sensors, by the engine controller in order to calculate the mass air flow rate into the engine. Such calculations are known as volume-density computations or speed-density computations.
Recently, air flow meters have been used with fuel-injected engines which directly measure air flow rates of induction air into the engine. For example, known air flow meters include suspended-plate-type flow sensors, swinging-gate-type air flow sensors, and mass-flow sensors. However, these flow meters provide additional bulk and make engines more expensive to manufacture.